> At each level a caller might need 5% of the functionality of any given dependency. The deeper the dependency tree gets the more waste piles on. Eventually you end up in a world where your simple binary is 500 MiB of code you never actually call, but all you did was take that one dependency to format a number.

I'm not convinced that happens that often.

As someone working on a Rust library with a fairly heavy dependency tree (Xilem), I've tried a few times to see if we could trim it by tweaking feature flags, and most of the times it turned out that they were downstream of things we needed: Vulkan support, PNG decoding, unicode shaping, etc.

When I did manage to find a superfluous dependency, it was often something small and inconsequential like once_cell. The one exception was serde_json, which we could remove after a small refactor (though we expect most of our users to depend on serde anyway).

We're looking to remove or at least decouple larger dependencies like winit and wgpu, but that requires some major architectural changes, it's not just "remove this runtime option and win 500MB".